Download 1 Subatomic Particles – Lets Review Again! General Information: An

115 PLTL Activity Sheet # 2
Subatomic Particles – Lets Review Again!
General Information:
♦ An atom is electrically neutral and consists of three subatomic particles.
♦ Proton – Positively charged subatomic particle found in the nucleus of an atom.
♦ Neutron – Neutral subatomic particle found in the nucleus of an atom.
♦ Electron – Negatively charged subatomic particle found outside of the nucleus in an
atom.
♦ Atomic Number (Z) - The number of protons (and electrons) in the nucleus of an atom.
♦ Mass Number (A) – The total number of protons and neutrons in the nucleus of an atom.
♦ Isotope – Atoms of an element having the same number of protons and electrons but different
number of neutrons.
♦ Average Atomic Mass = (Mass of Isotope # 1)x(Abundance) + (Mass of Isotope #
2)x(Abundance) + (Mass of Isotope # 3)x(Abundance) + ……
Activity 1
1. Fill in the blanks in the chart that follows. Be sure to include ionic charges when appropriate.
The first row is completed as an example.
Symbol
# protons # neutrons # electrons Atomic Number, Z Mass Number, A
63
29
34
29
29
63
29 Cu
27
7
45
53
54
+
Ag
99
68
Activity 2
1. Marble A has a mass of 10.00grams. Marble B has a mass of 12.00 grams. If you have 15 marbles
of type A and 75 of type B, what is the average mass for this collection of marbles?
2. Using your solution to the previous part as an example, write a general formula that can be used to
calculate the average mass for any collection of marbles A and B.
Some material adapted from Peer-Led Team Learning-Gen Chem, Prentice Hall (2006) and Chemistry A Guided Inquiry, John Wiley & Sons (2008)
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115 PLTL Activity Sheet # 2
3. The masses of the three naturally occurring isotope of magnesium are 24Mg (23.98504), 25Mg
(24.98584), and 26Mg (25.98259). Refer to the periodic table to determine which of the three is
most abundant. Can you determine which is the second most abundant? Explain.
Activity 3
1. There are two naturally occurring isotopes of boron. Their atomic masses are 10B (10.0129 amu)
and 11B (11.00931 amu). Without using a calculator, choose the best estimate among the following
for the percent abundances for the two isotopes. (Hint: Refer to the periodic table for the average
atomic mass of boron). Explain the reason for your choice.
a. 40% 10B and 60% 11B
b. 80% 10B and 20% 11B
c. 20% 10B and 80% 11B
d. 60% 10B and 40% 11B
2. Calculate the actual percentage abundance of the boron isotopes. How does your calculated value
compare with your estimate?
Activity 4
Your semester grade in Dr Harridan’s chemistry course is based on the following criteria:
Quiz 1
20%
Quiz 2
20%
Final Exam
60%
If your Q1 grade is 90 and your Q2 grade is 88, what grade do you need on the semester exam in
order to obtain an A (90 %) for your overall grade?
Some material adapted from Peer-Led Team Learning-Gen Chem, Prentice Hall (2006) and Chemistry A Guided Inquiry, John Wiley & Sons (2008)
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115 PLTL Activity Sheet # 2
Activity 5
The isotopes of oxygen are 168 O , 178 O , and 188 O . Oxygen-18 is particularly important because of its use
in medicine as a precursor for fluorine-18 (used in Positron Emission Tomography, PET) and as a
marker of temperature in studies of earlier climates on the Earth. Find the exact mass of this isotope
(oxygen-18) using the following information and the periodic table:
Symbol
Mass (amu) Percent abundance
16 O
15.994915
99.762
8
17
16.999132
0.038
8O
18
8
O
??
0.200
Some material adapted from Peer-Led Team Learning-Gen Chem, Prentice Hall (2006) and Chemistry A Guided Inquiry, John Wiley & Sons (2008)
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